Aircraft auxiliary landing gear



May 2, 1950 E. w. SHAW 2,506,178

AIRCRAFT AUXILIARY LANDING GEAR Filed March 7, 1946 5 Sheets-Shet 1 IN V EN TOR.

A TTORN E K .May 2, 1950 Y E. w. SHAW 2,506,178

AIRCRAFT AUXILIARY LANDING GEAR Filed March 7, 1946 5 Sheets-Sheet 2 IN V EN TOR.

fdnord (Ma/r m:

ATTORNEY:

y 2, 1950 E. w. SHAW 2,506,178

' AIRCRAFT AUXILIARY LANDING GEAR Filed March '7, 1946 I 5 Sheets-Sheet 3 H II.

lllll lllllllll lllll INVENTOR.

Ti fdrrardlifd/fian' ATTORNEY:

May 2, 1950 E. w. SHAW 2,506,178

AIRCRAFT AUXILIARY LANDING GEAR Filed March 7, 1946 5 Sheets-Sheet 4 a INVENTOR. I 3% [I'd/mm llf J/M/r BY a J/(AZM ATTORNEY y 2, 1950 E. w. SHAW 2,506,178

, AIRCRAFT AUXILIARY LANDING GEAR Filed March 7, 1946 5 Sheets-Sheet s 7a 99 M6 I IN V EN TOR.

AT ORNEY;

fiatented May 2, IQ SG AIRCRAFT AUXILIARY LANDING GEAR;

Edward W. Shaw, Babylon, N. Y., assignor to Re public Aviation Corporation,

Farmingdale,

N. Y., a corporation of Delaware Application March 7, 1946, Serial No. 652,603

20 Claims.

The invention relates to aircraft auxiliary landing gears, such as tall wheels, nose wheels, or tail skids, of the castering or swivelling type and proposes new and improved means to center and lock such gears in fore-and-aft alignment when swivelling or castering becomes objectionable or dangerous, as, for example, during certain phases of take-ofi and landing.

Although both manually and automatically controlled locking mechanisms have been previously proposed, they have not proven entirely satisfactory in actual practice. The main objection to manually controlled locking mechanisms for auxiliary landing gears is that they require an additional control lever or member in an already crowded cockpit, as well as additional cables, fittings and other connections between the landing gear and control member or lever in the cockpit and also require the attention of the pilot during take-01f or landing, i. 6. when he is most occupied in the actual control of the plane. Automatic locking mechanisms, unless provided with a manual emergency release, have been found objectionable because they determine too rigidly the periods when the gear is locked or is free to swivel and thus render taxiing hazardous under conditions where more flexibility is required or desired.

. The present invention is predicated on the known coincidence in the operation of the elevators and the locking of the auxiliary landing gear against swivelling, or of freeing ,it for castering. In landing or during take-off it isv desirable that the auxiliary landing gear (skid or nose or tail wheel) be locked against castering or swivelling in order to insure safe operation and to prevent yawing or ground loops: and in landing and during take-off certain conventional adjustments of the elevators are required. Therefore, it is proposed by the present invention to so coordinate the standard or conventional elevator control mechanism of an aircraft with the mechanism for locking the auxiliary landing gear against castering or swivelling that concurrently with the .required conventional adjustments of the elevators for orduring landing or takeofi the auxiliary landing gear is locked. Thus the objectionable rigidity of the prior auto-V. matic locking mechanisms .is avoided and the additional control member, cable connections and associated parts, customarily used in manually controlling the mechanism locking the auxiliary landing gear against swivelling, are eliminated. In this manner the present invention relieves the pilot of the burden of controlling the locking mechanism for the auxiliary gear at a time when he is especially occupied with the other manipulations and precautions involved in and coincident with take-01f or landing.

construction, combination and arrangement of parts, all as hereinafter more fully described, claimed and illustrated in the accompanying drawings, wherein: Fig. 1 is a side elevation of a retractable tail wheel assembly embodying the present invention; illustrating the wheel protracted and the asso-' ciated aircraft parts in section.

Fig. 2 is a similar view showing the tail wheel assembly of Fig. 1 in its retracted position:

Fig. 3 is an enlarged side elevation ofa part of the housing and mounting for the spindle of the tail wheel and associated external elements as viewed from the side opposite of these parts to that shown in Figs, 1 and 2: Fig. 4 is a vertical section taken along line 4-4 of Fig. 3 to illustrate the details of the tail-wheel spindle and the lock by which it is fixed or seecured against swivelling or castering: Fig. 5 is a vertical section of the cam plate shown in its operative position in Fig. l wherein the cams appear in elevation:

Fig. 6 is a vertical section taken along line B-B of Fig. 52 j Fig. 7 is a plan view' of the interconnected com} ponents of the locking mechanism and of the elevator control mechanism whereby the operation of these mechanisms is coordinated: and Fig. 8 is a side elevation of the interconnected components of the locking mechanism and of the' elevator control mechanism as shown in Fig. 7.

Referring to the drawings, the present inven' tion is illustrated as embodied in an aircraft having a fuselage In (part of the tail structure of which is shown in section). ture I0 includes a rear bulkhead H, carrying an upper bracket I2 and a pair of horizontally aligned lower brackets l3 disposed below and within the same vertical plane as the upper bracket 12, and a tubular support It mounted horizontally across the fuselage l9 aft of and substantially parallel to the bulkhead l I. On this support I4 is medially fastened a sleeve 15 by means of screws or rivets l6 (Figs. 7 and 8). This sleeve l5 carries two parallel arms i1 and I8 spaced one from the other longitudinally of the sleeve and projecting radially and rearwardly This tail struce linkage that are necessary to an understanding wheel support and retracting assembly comprising a V-shaped yoke 22, a tubular spindle housing 23, welded to the apex of the V and a spindle normally free to swivel within said housing and provided with an ofiset lower knuckle 24 adapted to receive and mount a tail Wheel 25.

To the apex of the V-yoke is welded or o'therwi'se secured an upwardly extending lug 26, the outer extremity of which is pivotal'ly connected through a universal joint 21 to the cylinder 28 of an oleo shock absorber. 29 of .the shock absorber is pivotally connected, by means of a universal joint 32, to one corner of a generally triangular strut 3|. This strut 3| has another corner 32 pivoted to the upper bracket pivoted by means of a universal joint 33' to the piston 34 of a hydraulic retracting motor 35, hinged to a fixed part of the fuselage lil by any suitable means, such as the bracket 35. Adjoini-ng its connection to the plunger 29 of the shock absorber the strut 3| carries a hook 3'! to which is anchored the fore end of a 'coil spring 38, the rear end of which is anchored to an eyebolt 39 piercing and secured to the tubular support Hi. When the tail wheel is in its protracted position (Fig. 1), the oleo shock absorber 2829 and the long side of the triangular strut 3| are aligned and form the links of a toggle mechanism which is kept on dead center by the coil spring 38 as sisted by the retracting motor 35, then hydraulically locked in the extreme extended position (it its piston 34. The retraction of piston 34 within the cylinder of the hydraulic motor 35 to the position shown in Fig. 2 breaks this toggle against the action of the spring 38 and swings the yoke 22 counterclockwise about its pivots 22'- thereby retracting the wheel 25 into the fuselage l0 (Fig. 2). I

The tail wheel spindle (Fig. i) comprises a collar a lower journal 4! formed above said collar to cooperate with a lower bearing 42 secured in the bottom 33 of the housing 23, a spline M on which is slidably mounted, an internally splined sleeve 45 having an annular flange 46', an Upper journal 41 positioned above the spline 44 to cooperate with an upper bearing 43 and 'a threaded end portion 19 on which is screwed an assembling nut 55. The upper part of the post or housing 23 is closed by a circular cover or cam plate 5| extending into the housing 23 and having an outstanding flange 52 seated in agrec ess or groove 53 formed in the inner wall of the housing 23 adjacent its upper end. The bottom or inner surface of this cover orplate 5| in the form of a continuous cam surface or track composed of two oppositely disposed semn circular double ramps 54 and 55 combining to from a cam lobe and having their adjoining lowermost bottom-ends 56 aligned radially along a lower diameter of the plate 5| and their re spective apices 51 and 58 aligned along an upper The telescopic plunger I2 while the remaining corner 33 is diameter of the plate 5| perpendicular with respect to said lower diameter. As a bearing for the journal 41 adjacent the outer extremity of the spindle, a bushing or collar 38 is pressed into a central concentric opening in the cover or cam plate 5| and at its end is provided with an outstanding flange 58'. When the bushing or collar 48 is in its operative position it' is rigidly assembled with and surrounded by the "cover or .cam plate 5| and its flange 48 rests coplanar ahd coextensive with the flange 52 and on that edge of the plate 5| defining the central concentric opening through which the bushing or collar 48 passes.

Surrounding the spline i iof the spindle is a sleeve 45, internally splined for reciprocating cooperation with spline 34 and provided with a flange 46 at the end thereof toward the bushing or bearing 38. At its edge and within the housing 23 the flange 55 is provided with a lip 46 lying parallel to and spaced from the sleeve 45. On the face of flange $6 of the sleeve '35 opposed to the lip 46 are rigidly mounted a pair of diamet= rically opposed U-brackets 59 each supporting a roller 60 rotatably mounted on a rivet 5| secured through the arms of the coacting bracket. These 23 is an inwardly extending shoulder or shelf 63,

on which is secured, by the countersunk rivets 64, a fixed friction ring 55. The spline d4 slidably carries near its lower end an internally spli'ned sleeve 86 having an annular flange 5| on which bears the lower extremity of the spring 62. The lower flat face of this flange 5'1 acts as a pressure ring in cooperation with the friction ring to dampen progressively the swivelling motions of the wheel 25 out of its neutral or fore-and-aft aligned position in either direction. In the neutral position of the self-centering device shown in Fig. 4, which corresponds to the fore-'- and-aft aligned position of the wheel 25, there is suiflcient energy in the spring oz to maintain the rollers 50 tightly pressed against the apices 5'! and 53 of the cams or ramps 5-5 and 55 and to press the ring 6'1 strongly upon the friction ring 65, thus damping any tendency of the wheel 25 to flutter or shimmy at the inception of said undesirable oscillations.

The interior of the housing 23 is protected at its top against entry of foreigninaterial by means of a dust cover 68 held between the nut 5|] and the flange 52 of the cam plate 5! and the flange 48 of the upper bearing 58. At its bottom a packing ring 69 surrounds the lower bearing 42 and is compreszed between the bottom #33 of the housing 23 and the collar '43 of the knuckle 24 when the device is assembled with the nut 50 in its operative position. Thus the lower end of the housing 23 is protected from the entrance of foreign matter.

To the periphery of the collar til is fastened or attached an annular flanged ring ll having a circular bolt hole i3 tapered or flared at its entrance !4 and surrounded by a boss 12 on the underside of the ring 1|. As will be described more in detail it is by means of this ring ll fixed to the collar 16 and by it to the spindle 4 I-"fl-fl that the tail Wheel 25 and its associated parts may be locked against castering or swivelling.

A tubular bolt casing having an external and integral lateral boss 16 to be engaged in a peripheral groove 11 in the wall of the housing 23 at or near its bottom 43, is welded or otherwise fixedly secured to one side of the housing 23 with its axis parallel to the axis of the spindle 4I--4441 and in vertical alignment with the bolt hole 13 when the wheel is situated in substantially true fore-and-aft position, i. e. when the parts associated with the spindle are relatively situated as shown in Fig. 4.

The hollow bolt casing 15 is partly closed at the end thereof remote from the ring 1| and its flared bolt hole 13 by the centrally and concentrically apertured end wall 18.. Within the aperture of the end wall 18 is a liner or bushing 19 and a similar liner or bushing 80 is positioned within the bore of the casing 15 to extend from the inner face of the end wall 18 to the lower extremity of the casing. A bolt 82 having a slightly tapered end portion 85 is mounted for reciprocation in the casing 15 so that when the the casin and through the passage 83 in the bolt to be threaded into the socket in the bottom of said passage thereby to attach the stem to the bolt all as illustrated in Fig. 4. Between the inner face of the end wall 18 and the bottom of the passage 83 a compression spring 84 is housed in said passage 83 and encircles the stem 8|. This spring urges the bolt 82 and its stem 8| downwardly in the casing 15. Th tapered end portion 85 of the bolt 82 when abandoned to the action of the spring 84 is projected into hole 13 of the ring 1| to lock the wheel 25 in exact foreand-aft alignment and due to the flared entrance 14 of the opening 13 this projection of the end 85 of the bolt exactly centers the wheel even if it is slightly out of alignment at the beginning of the movement of the bolt.

Normally the tail wheel 25 is free to swivel or caster, as the bolt 82 is kept in its retracted or non-projected position within the casing 15 by a coil spring 86 capable of overcoming the action of the looking or projecting spring 84. .This spring 86 surrounds the portion of the stem 8| extending beyond the end wall 18 and operates between the outer face of said end wall and a sleeve 81 slidably mounted onthe stem 8| of the locking bolt 82. Hence this sleeve 81 is urged by the spring 86 to the outer end of the stem 8| where it abuts a nut 88 adjustably threaded on the extremity 89 of the stem 8| and thereby retracts the bolt 82 inwardly of the casing 15 against the action of the spring 84 until the inner end thereof contacts the underface of the end wall 18. The elements are shown in this retracted position of the bolt 82 in Fig. 4.

To operate the bolt 82, against the action of this retracting spring 86, when it is desired to lock the Wheel 25 in fore-and-aft alignment, use is made of the push-pull rod system or linkage controlling the movements of the elevators from the cockpit of the aircraft, only the links 20 and 2| and thelast idler I9 of which are shown in Figs. 1, 2, '1, and 8.

To that end the idler I9 is provided with an 6 gral radial arm 95 located centrally betwefi.

its ends and which is fixedly attached to one end:

of a hub 91. This hub 91 pivotally embraces the bolt I9 secured to and extending between the arms 95 and 96 are traversed by a boltv 94 which protrudes beyond the outer face of thearm 98 and there pivotally supports a roller or cam fol-- lower 9 I. I5 adjoining the arm I8 is a vertical bracket plate II and adjacent to the extremity thereof is supported a lever 99 pivoted medially of its ends, as at IIlII, to said bracket plate. A cam 99 is riveted or otherwise secured, as at 98, to one face and at one end of the lever 99 and comprises two curved tracks I02 and I83 (Fig. 8) the first of which is concentric to the pivot bolt I9- in the angular position of the lever 99 shown in Fig. 8 and the second of which is concentric to the pivot bolt I9 in the angular position of the lever. 99 shown in Fig. 1. These two tracks I 02 and I83 are joined by a ramp I05 thereby combining to constitute a continuous cam projecting below the lower edge of the lever 99.

A coil spring I95, attached at one end to an anchor plate I 91 secured to the fixed arm I8, and at its other end to the end of the lever 99 on the opposite side of the pivot I98 to the cam 99, tends constantly to swing the lever 99 clockwise about said pivot I00 to maintain the cam 99 in operative engagement with the roller or cam-follower 9|.

1 That end of the lever 99 remote from the cam has one end of a cable 92 secured thereto by any suitable means, as for example the clevis I08- This cable 92 is reeved over the pulleys I99 and III! mounted on the bulkhead II and over the pulley I mounted on the yoke to terminate in proximity to the outer end of the bolt stem 8|. The function and purpose of the cable 92 will be hereinafter set forth in detail. The relative positions of the pulleys I09, III] and III withrespect to the pivot 22' of the yoke 22 is such that the normal tension of the cable is not substantially afiected by the angular or swinging movement of the yoke 22 about the pivot 22' when the wheel 25 is being either retracted or protracted.

- On that side of the housing 23 adjoining the casing 15 is fixedly secured an upright II3 by means of rivets I I2 which carries at its upper enda grooved baflle or deflector II 4 fastened thereto by means of the rivets II5. This deflector Ill. is so associated with housing 23 and with the cable 92 that it lies at all times in the verticalplane of the cable 92 so that when the wheel 25 is retracted, as shown in Fig. 2, the cable will seat in the groove H4 in the edge of the deflector. The upright II3 has a lateral extension H6 at its lower end to project beyond the housing 23 where it pivotally supports a bell-crank lever 93 on a pin I I1 traversing said extension H6 and the elbow of the bell-crank 93.

One arm of the bell-crank 93 normally occupies a generally horizontal position and terminates in a fork II8 one branch of which lies on each side of the sleeve 81. Each branch of this forked end I I8 is in turn bifurcated as at II9 (Figs. 3 and 4) to embrace a stud I29 secured to the sleeve 81.. The two studs I20 are aligned transversely of the sleeve 81 on either side of the stem 8| but are not connected at their inner ends with the result that the stem 8| and the bolt 82 may move freely:

Rigidly secured to the stationary sleevewitnteeeeet te the sleeve a'i. '1 neether armei tfiiibel-l' erafik it is substantially vertical a'n'dt'er- Initiates somewhat elieve the upper end of the helliifig fi; "That te'nnmal of the cable 92 extending-beyond the pulleylll is attached to the eittreini'tyof the-vertical arm of the beuwrank 93 se that it may estimate said bell-crank in the manner and for the purposes here-matter setforth. operation of the present cofnbind'eenter ing-ziampmg and ioeking meehamsm for aligning the tail Whee1 in for-anii aft position Cbortililatio'n theadjn'tfint of the elevatere is-asronows;

IfYafi-ifi'i a1 positien where the tail Wheel 25 is prtra'ctedand the ele'tatoi'sa're in neutral, with the c emponems ias'are shown in Figs 1, s and 4, tti 'fioller Q-I is looaited under the tia'ek or section l fli bftlie cam to am: as a Stob in preventing me pring It? from exefti'ng an Operating pull 0H tli eabl 92 and the bolt 32 is mate in its e:-ti=e1i' ae i'etr aeted position by the sp ing as operating between the end Wall 180i the casing 1-5 anu thesleeve B1; The length of the Cable 92 is seen-that thefe is no appreciable slack therein when the parts are in these positions and the wfieelii and it's spindle 4t-4i- 44 '41ere free te--easte r or swivel in the bearings and 42 in the housing 23.

When 'takiiiig to a take-01f with the tail Wheel free to swivel and the elevators in neutral, the-p lot always manipulates the stick or Control to adiustthelevators in order to keep the tail ottne snip -down. The links is, 2% and 2| and the rene'r 9| are-thereby 'moved from the position of Fig; 1 into the position of Fig. 8. The lever Slat this'ti'me is momentarily abandoned tothe combined action of the springs H35 and 84 and swings- Clockwise about its pivot QB While the roller -9l rides over the ramp I to the cam tf-aek'TOZ; As the earn track N12 is then concen trio to the-pivot IQ of the idler l9 and itsrradial; arm no further relative angular movement of the lever 99 occurs when and as the roller 9| trav'e'Isalongthis-cam track [02. This swinging movernen'tof the lever 933 is transmitted through the tautcable 92 to the bell-crank eto swing it simultaneousl -and Slide the sleeve 8? downw rdly against the action o-f-the-sp'ring se. The makingbolt'82 isthereby abandoned to the action or the springtd'andits tapering point 85 is projected into the hole T3'if during taxiing the Wheel 25 is -a1ig ned fore and aft, or rides on the ring H, ready-to enter said hole 13 as soon as alignmentoff'the-holt -i and hole "J3 is'established. As the pilot always straightens his course near the end. of the taming run the locking bolt 8 2will ultilea-bay align with thehole'i? prior to actual takeo ff riin; Durin'g'this'ruri to a take-cit, the spring 62-actsc nstant1y on the one hand, through the. self-centering cams 55' and 55 and'cam followers; ogjrollers fifl, to urge thewheel 25 back in its foreand-aft aligned position and, on the other hand; through the damping device 55 and $1, to prevent" or minimize any tendency of the Wheel to oscillate or shimmy.

' Thus; the tail Wheel 2'5 is always looked in its fore and-aft position immediately-before and during the -actual take-off run and take oif and" remains positively looked in this position during the-entireensuing fiight when the present iii-- vention and its components has no effect or-irr fiu'e'hee on the movements or operations of the elevators due to the fact that the active SilifaGe llzze-ioa' lo's of the care fill fe'niaifi's out eithei Q'fiiflaflii'aith niche-roller 9| due to the movee iv iposition shown inFig. l. .asy thetailwheel i Btoiiches'the groundi the pilot riient 'iif'the idler 'lezabout the center 'I 5 as 16118: as the tail wheel iszret ractedintotheifuselage1H).

This disabling of the mechanical-connection be tween the --'elevator controlmech'anism and the tail Wheel locking mechanism :is automatically efiected uponxretraetionof the tail wheel hyithe action of -the balile i In which deflects theicable,

92 as shown in Fig; 2 tos wingthe bell crank-SS about its pivot ii i and compress thespning; 86". As-th'isaction does not permit further lowering ofthe' sleve 81 and further rotation/of the Joelldrank 93 about the pivot 'l H, this defiectio'niof the' dabl'e 9'2 i-esnltsdn' a downwardpullwhich.

swings the lever 99 against the actionroftth. spring 4% teen angle sufiieient to raise the, bottorn'of -the ramp-Miami the *cam iflfiabovethe path of-end'nutof contact with the roller 91.

When-,Sprior tc) landing withthe elevators 'down, the pilot lowers'the tail Wheel 25,:the :bafile H! is withdrawn from i'tinder the caiole 92 thereby; abandoning it to the: simultaneous *ac'tion' map: posrte directions of the springs IE5, '84 and zof;

the' spring 86. While the pull of'the spring 86 then swings the bell-crank 93 in the reverse direction and Withdraws the locking pin fifitr'oml the: hole 53; thereby unlocking the -tail 'wheelfifi, theipu'll'due'to the'combined ac'tioniof the springs 1'66 and 3d swings the iever 99 Jclockw-ise "(Fig. 12') until the-Garnet! contacts and rides on the roller 5H As longa's the ipilet keeps theelevators down and even if he varies their angular position of adjustment, the roller 9 i rides over the track '13 without afiecting theangular. @position of the lever 99,-as the track 103 is 'Ethe'n concentric'twthe pivot 1 9 of the idler 4 9. Thoughv during this short peri'od -'of descent with the l'andin'g gear :down, the tail wheel is unlocked, it "will not *deviate from its-ipositionof fore-and-iaft alignment vdue to the "centering action of thewspringtfi.

'Wl'ien the pilot adjuststhe elevators to level-- ofi for alan'dinggthe roller 9! r eturnsin its new t'ral i'position, 'su'bstantially 'in the vertical plane :of the pivot l S and all themarts I o f fthe a'swivel- .lock =mechanisn1 a'rewback in the initial unlocked Just beforegzor :;as soon :aIdill'StS tIIG eTeVHtOI-E Keep the tem (if th'e craft (down, and by that actionre loeks thetail whel as has-been described above and as'shownparitially in f'F'ig-S. 7'1 and- 3.

Ihus the tail wheel 25 isalways lockedri'n'iits ror'e-iand-ait en ma position during the actual landing operation and'r'emains "positively locked eally -ineifetiv e.

It must be observed thatjdue' to th-is'proximity of the-"ramp fileof the camefitoth-e neutral position of the roller =9! tFig. 1),--a "relatively sn-iallangular dishlacement of the control lever froin neiitra'l ('of the orderof afew degrees) will sufice to effect *this looking'of the tail wheeli i upon "adjusting the elevators through a correspondingrlatlvly small angle. Further adjust- .ment of the elevators has no effetonthewail" fihe'el iocliing 'mechanismfas the-"roller "9 I merely rides over track I 02 without resulting in any relative angular movement of the lever 99.

Inversely, when the pilot returns the control lever to neutral, nothing happens to the tail wheel locking mechanism as long as the roller 9! merely'rides over and on track I92, but a few degrees before reaching its neutral position, the roller 9! rides on the ramp N15 to move the lever 99 against the action of the spring I06 and thereby allows the unlocking of the tail wheel to take place under the action of the spring 35.

While the present invention has been shown and described in detail as applied to a tail wheel or skid of an aircraft, it is to be understood that it can as well be adapted to the castering or swivelling nose wheel of a tricycle landing-gear.

What is claimed is: I

1. The combination with an aircraft having a manual control system to adjust the elevators thereof, of a swivelled auxiliary landing gear, a mechanism to retract and protract said landing gear, latching mechanism positively locking said gear against swivelling, a mechanical connection between the control system and said latching mechanism for coordinating the operation thereof with the operation of the elevator control system during landing and take-off, and means, responsive to the operation of the retracting mechanism, to render said mechanical connection inoperative during flight.

2. In an aircraft, the combination with an elevator control system, of a retractable auxiliary landing gear comprising a yoke mounted on a fixed pivot on the aircraft, a housing rigid with said yoke, spindle and knuckle mounted to swivel in said housing, and an auxiliary wheel mounted on said knuckle, a mechanism coacting with said yoke to retract and protract said wheel, a latch positively locking said spindle against swivelling movement in said housing and thereby secure said wheel in fore-and-aft alignment, means interposed between said elevator control system and said latch to render the latch effective upon the adjustment of said system to set the elevators for'take-offor landing, and means, responsive to the operation of said retracting and protracting mechanism, for rendering the last said means ineffective during flight.

3. In an aircraft, the combination with an elevator control system, of a retractable auxiliary landing gear comprising a yoke mounted on a fixed pivot on the aircraft, ahousing rigid with said yoke, a spindle and knuckle 'mounted to swivel in said housing, and an auxiliary wheel mounted on said knuckle, a mechanism coacting with said yoke to retract and protract said wheel, a latch positively locking said spindle against swivelling movement in said housing and thereby secure said wheel in fore-and-aft alignment, means interposed between said elevator control system and said latch to render the latch effective upon the adjustment of said system to set the elevators for take-off or landing, and means, responsive to the operation of said retracting and protracting mechanism, for rendering the last said means ineffective upon the retraction of said landing gear during flight and to restore its effectiveness upon the protraction of said landing gear for landing.

4. The combination with an aircraft having a swivelled auxiliary landing gear and means for adjusting the elevators thereof, of a housing, a splined spindle carrying the auxiliary landing gear journaled in said housing, a centering bearing means slidably splined to said-spindle adja 10 cent one of its ends, an annular brake member fixed to that end of said housing remote from said bearing means, a slidably complemental brake member splined to said spindle, a spring situated in said housing and interposed between said slidable bearing means and said slidable complemental brake member and thereby urge the auxiliary gear to fore-and-aft alignment and simultaneously reduce shimmies or oscillations thereof, a locking mechanism for positively fixing the spindle against swivelling movement in said housing and thereby lock the gear in fixed foreand-aft alignment, and means associated with the means for "adjusting the elevators and ar ranged to render said locking mechanism effec tive upon the adjustment of said elevators for landing or take-01f.

'5. In an aircraft, the combination with a swivelled auxiliary landing gear, of a housing carried by the aircraft, a splined spindle supporting said gear journaled in said housing, a plate having internal cam surfaces surrounding said spindle and secured against movement to one end .of the housing, a splined sleeve slidable on the spline of the spindle adjacent the plate aforesaid and having bearing members coacting with the cam surfaces of said plate, a stationary brake member attached to the inner face of the housing at the end thereof remote from said plate, a complemental brake member splined to and slidable on the spline of the spindle, and a spring interposed between said sleeve and said complaimenta] brake member to urge and maintain the bearing members of the former in operating contact with said cam surfaces and the comple mental brake member in operating engagement with said stationary brake member.

6. The combination with an aircraft having a control system to adjust its movable control surfaces, a swivelled ground engaging member and a mechanism to retract said member, of a locking mechanism to positively and automatically secure the auxiliary ground engaging member in foreand-aft alignment and against swivelling movement, aconnection for rendering said locking mechanism effective upon the operation of the control system to adjust the movable control surfaces for take-off and landing, and means automatically responsive to the operation of the retracting mechanism to render said connection inoperative during flight.

7. The combination with an aircraft having a push-pull rod system to adjust its elevators, a tail wheel mounted to caster, and a mechanism to retract and protract said tail wheel, of a locking mechanism to secure said tail wheel in fore- .and-aft alignment, a mechanical connection interposed between said locking mechanism and the push-pull rod system to adjust and render said locking mechanism effective upon the adjustment of the system to set the elevators for take-off or landing, and means, responsive to the operation of the retracting and protracting mechanism, to render said mechanical connection inoperative upon retraction of the tail wheel.

8. The combination with an aircraft having a rigid push-pull rod system including a pivotally mounted idler for the adjustment of its elevators and a swivelling tail wheel, of a roller carried by said idler of the push-pull rod system, a lever pivotally mounted on the aircraft structure to be swungtoward and away from said roller, a two- 'stage cam on one end-arm of said lever whereby either stage of said cam may be situated concentric to the pivot of said idler to cooperate v 1'. with saidroller, a spring constantly urging said cam into engagement with said roller, a sprin actuated bolt coasting with said tail wheel for positively and automatically locking it in foreand-aft alignment, and a cable connection between said bolt and the end of said lever opposed to that carrying said cam by which the oscillations of the lever by the movement of said roller relatively to the cam determines the eifectiveness and ineffectiveness of the spring actuating said bolt, 9. The combination with an aircraft having means for controlling its elevators, of a tail Wheel swivelled in a, yoke mounted for pivotal movement in a vertical plane/a mechanism to retract and protract said tail wheel, a spring bolt to lock the tail wheel against swivelling movement'relatively to said yoke, an antagonistic spring normally keeping said bolt" in inactive position; compression means for disabling said antagonistic spring, a lever" responsive to the movements of the elevator controlling means, a cable connection between said compression means and said lever, tensioning means to keep said'cable connection constantly taut, and defleeting means carried by the yoke toswing said lever. out of engagement by the elevator controlling means uponretractionof thetail wheel.

10. In anaircraft, the combination with the push-pull'rodsystem for'the adjustment of the eievatorsof' the aircraft, of-"an idler interposed between and connected'to components: of said system,.a fixed structural element, spaced arms rigidv with said element and extending. laterally therefrom, a hub pivotally mounted between the extremities of said arms h'aving'the idler of the push-pull .rod system fixed to and suspended from. one of its ends, a radial arm secured to the other end of said hub and terminating adjacentsaid idler, 'a' roller journaled adjacent said arm on an. axis normal to the radial arm and to the idler medialof its length and arranged to swing with said idler as it moves during the adjustment of the push-pull rod system to regulate the elevators,v a vertical bracket plate secured to said structural element at right angles to the spaced arms. aforesaid, a lever pivoted centrally of its lengthto. said bracket, a two stage cam fixed to one end of said. lever and located above said roller, the stages of said cam being. connected by a ramp, a spring int rp s between the opposite end of'saidlever. to constantly urge said cam toward said roller, a retractable tail wheel provided with a castered mounting, a spring, actuated lock to secure said tail wheel against castering, a cableconnected .tothat end of the lever. opposed to said cam and leading to said lock, and means associated with said lock and under the control of said cable to oppose the spring. actuation of the lock and'to abandon the lock to its sp in a ua up the operation of 'the push-pull rod system to adjust the elevators and simultaneously oscillate said lever through the medium of the coaction between tliecam and roller asaforesaid, ILIn an aircraft, the combination with the push-pull rod system for the. adiustment'oi' the elevators of the aircraftxofian idler interposed between and connected to components of said system, a fixed structural element, spaced arms rigid with. said element and extending laterally therefrom, 'a hub pivotallymounted' between the extremities of said'arms h'avingthe' idler of the push pull' rod system fikedfio and suspended lrom'one of its endaa'radial arm secured'to the other end of said hub and terminating-"adjacent said idler, a roller journaled adjacent said arm on an axis normal to the radial arm-andto the idler medial of its length and arranged to swing with said idler as it moves during the adjustment of the push-pull rod system to regulate the elevators, a vertical bracket plate secured to said structural element at right angles to the spaced arms aforesaid, a lever pivoted centrally of its length to said bracket, a two stage-cam fixed to one end of said lever and'loe'ated above said roller, the stages of said cam being connected by'a ramp, a spring interposed between theopposite end of. said lever'to' constantly urge said'cam toward said roller, a yoke pivoted to the aircraft, a housing fixed to the' yoke, a tail wheel, a spindle. carrying said tail-wheel mounted to caster in;said housing, a bolt casing fixed to said housing, a bolt mounted to reciprocate in said casing for projection into locking engagement with said spindle, oppositely acting'springs cooperating with said bolt,.one to project the bolt. and. the other to retract it against the-ac:- tion of" the projecting spring, and connection between that end of the aforesaid leveropposed to said cam to render said retracting spring in"- effective upon the oscillation of' the lever by means of the coaction between the cam and roller upon the operation of the push-pullrod system.

12. In an aircraft, the combination with the push-pullrod system for the adjustment of, the elevators of the. aircraft, of an idler interposed between and connected to components. of said system, a fixed structural element, spacedarms rigid with said element and eXtending'lat-erally therefrom, a hub pivotally mountedbetween the extremities of said arms. having the idler'of the push-pull rod system fixed to. and'suspended from one of 'it's'ends, a radialarmsecured to the other said idler as it moves during the adjustment of the push-pull rod-system to regulate the elevators, a' vertical bracket plate secured to said structural element at right angles'tothe spaced arms aforesaid, a lever pivoted centrally of its length to said bracket; a two stage nam fixed to one: end of said lever and located above said roller, the stages of said cambeing'connected by a ramp, a spring interposed between the opposite end of said lever to constantly urge said cam. toward said'roller, a yoke pivoted, to the aircraft, a housing fixed to the yoke, a tail'wheel, a spindle carrying said tail-wheel mounted to caster in said housinga bolt casing iiXedto'said-housing', a bolt mounted to reciprocate in said casing' for projection into locking engagement with said spindle, oppositely actin springs cooperating with said bolt, one to project the bolt and the other to retract it against the action of the projecting spring, a cable attached to that end'of the lever opposed tosaid' cam and extending to said bolt, and a connection between said cable and said retracting spring whereby upon the operation of" the l'everbythe coaction between asst-m 13 i between and connected to components of said system, a fixed structural element, spaced arms rigid with said element and extending laterally therefrom, a hub pivotally mounted between the extremities of said arms having the idler of the push-pull rod system fixed to and suspended from one of its ends, a radial arm secured to the other end of said hub and terminating adjacent said idler, a roller journaled adjacent said arm on an axis normal to the radial arm and to the idler medial of its length and arranged to swing with said idler as it moves during the adjustment of the push-pull rod system to regulate the eleva- .tors, a vertical bracket plate secured .to said structural element at right angles to the spaced .arms aforesaid, a lever pivoted centrally of its a ramp, a spring interposed between the opposite s end of said lever taconstantly urge said cam toward said roller, a yoke pivoted to the aircraft, a housing fixed to the yoke, a tail wheel, a spindle carrying said tail-wheel mounted to caster in said housing, a bolt casing fixed to said housing, a bolt mounted to reciprocate in said casing for projection into locking engagement with said spindle, oppositely acting springs cooperating with said bolt, one to project the bolt and the other to retract it against the action of the projecting spring, a cable attached to that end of the lever opposed to said cam and extending to said bolt, a sleeve slidably mounted on said bolt to abut the retracting spring and through which said retractin spring acts on the bolt, and a bell crank pivoted on said housing having one arm connected to said sleeve and the other connected to said cable so arranged that when the roller operates against one stage of the cam the lever aforesaid may be oscillated to swing the bell crank about its pivot and thereby functionally disconnect the sleeve from the bo t.

14. In an aircraft, the combination with the push-pull rod system for the adjustment of the elevators of the aircraft, of an idler interposed between and connected to components of said system, a fixed structural element, spaced arms rigid with said element and extending laterally therefrom, a hub pivotally mounted between the extremities of said arms having the idler of the push-pull rod system fixed to and suspended from one of its ends, a radial arm secured to the other end of said hub and terminating adjacent said idler, a roller journaled adjacent said arm on an axis normal to the radial arm and to the idler medial of its length and arranged to swing with said idler as it moves during the adjustment of the push-pull rod system to regulate the elevators, a vertical bracket plate secured to said structural element at right angles to the spaced arms aforesaid, a lever pivoted centrally of its length to said bracket, a two stage cam fixed to one end of said lever and located above said roller, the stages of said cam being connected by a ramp, a spring interposed between the opposite end of said lever to constantly urge said cam toward said roller, a yoke pivoted to the aircraft, a housing fixed to the yoke, a tail wheel, a spindle carrying said tail-wheel mounted to caster in said housing, a bolt casing fixed to said housing, a bolt mounted to reciprocate in said casing for projection into locking engagement with said spindle, oppositely acting springs cooperating with said bolt, one to project the bolt and the other to retract it against th action of the projecting spring, a cable attached to that end of the lever opposed to said cam and extending to said bolt, a sleeve slidably mounted on said bolt to abut the retracting spring on one of its sides and to abut a projection fixed to the bolt on the other of its sides thereby subjecting the bolt to the action of the retracting spring upon contact between the sleeve and projection, a bell crank pivoted to the housinghav ing' one arm connected to the sleeve and its other arm connected to the cable whereby the oscillation of the bell crank by and through the cable moves the sleeve out of engagement with said projection, and means carried by the housing to engage the cable upon the retracting movement of the yoke and thereby swing'the lever against the action of its spring and remove the cam from operative contact with the roller.

15. The combination with an aircraft having a fuselage, a rigid push-pull rod system to control its elevators, and a swivelled tail wheel of a sub "stantially horizontal structure fixed across the aft portion of the fuselage, an idler incorporated in the push-pull rod system at its lower end and having its upper end'pivotally suspended on said structure, a roller carried on one side of said idler, a lever mounted on said structure for pivotal movement in the plane of motion of said roller, a cam fastened to one arm of said lever to cooperate with said roller, a spring anchored to said structure and connected to the end of the said lever opposed to said cam, a locking mechanism to secure the tail wheel in fixed foreand-aft alignment, upon the movement of the push-pull rod system to adjust the elevators, and an operative connection between said mechanism and the upper arm of said lever.

16. The combination with an aircraft having a. system for the adjustment of its movable control surfaces, a swivelled ground engaging member, and a retracting mechanism for said member, of a normally inoperative locking mechanism associated with said ground engaging member which when operative secures it against swivelling movement, means operable by and from the system aforesaid to render said locking mechanism operative upon the adjustment of the movable control surfaces, and means effective in response to the operation of said retracting mechanism to render said locking mechanism operative independently of the system for adjustment of the control surfaces.

17. The combination with an aircraft having a system for the adjustment of its movable control surfaces, a swivelled ground engaging member including means to automatically center it in fore and aft alignment, and a retracting mechanism for said member, of a normally inoperative locking mechanism associated with said ground engaging member to secure it against swivelling movement when centered in fore and aft alignment, means responsive to the aforesaid system for establishing the operation of said locking mechanism upon an adjustment of the control surfaces, and means operable in response to the operation of the aforesaid retracting mechanism to establish the operation of said locking mechanism independently of said system.

18. In an aircraft including movable control surfaces and a linkage system for the adjustment thereof, the combination with an auxiliary landing gear mounted on the aircraft for swivelling movement relative thereto, of a locking mechanism engaging and holding said auxiliary landing gear against swivelling movement, arresting means preventing the engaging and holding operration of said locking mechanism, and means under the control-oi said linkage system to release said-lockingmechanismfrom the action of said arresting-means.

19. In. an aircraft including. movable control surfaces and-a linkage system-for the adjustment thereof, theeombinationwith a-housing", an auxiliary landing gear mounted to swivel in said housing, of alocking mechanism to secure said landing. gear against movement in'its. housing, means. holding said locking mechanism nor.- melly in an inoperativeposition, andmeans-inqterposed. between the locking mechanism and the-linkage system aforesaidto releasesaid locking-mechanism and thereby secure the. landing gear against .movementrelative to its; housing upon the adjustment. of the linkage system. to regulate the movablecontrol 1 surfaces.

2 Q. In an; aircraft, the. combination; with a linkage system for the adjustment of a control surface-thereof; of a swivelledauxiliary landing gear acontrollable locking means .securing said auxiliary landing gear against swivelling, re.- straining means rendering said locking means 16 inoperative, and a control for said. restraining means interposed between said linkage system and said restraining-means, whereby said (locking means becomes operative and the auxiliary gear locked against swivelling upon the operationeof the. linkage system in one direction.

EDWARD-W. SHAW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,674 Noonan Sept. 18,1945 2,192,282 Warner- Mar. 5,,19i0 2,333,550 Parker Nov. 2, 1943 2,379,173 Miller June 26, 19.4.5 2,385,89L Swanson Oct. 2, 1945 2,454,658 Leitch Nov. 23, 1948 FOREIGN PATENTS Number Country Date 700,660 Germany Dec. 27, 1940 

